1. Technical Field
The present invention relates generally to a method and apparatus for detecting when a defect is present in an image capture device such as a scanner and when maintenance is required. More particularly, the present invention relates to a method and apparatus for detecting a defect in an image capture device that can distinguish between an defect in the image capture device and one on the imaged object; and a method, apparatus and computer program product for detecting when maintenance is required.
2. Related Art
Digital imaging of documents, photographs and other objects provides numerous advantages including the ability to easily process, analyze and communicate images. One common method of creating a digital image is scanning using an image capture device such as a scanner. An image capture device typically includes a bar, or line, of illumination and a plurality of sensing elements such as a charge-coupled device (CCD). The sensing elements create the digitized image of the object. There are a variety of different type image capture devices such as a desktop flat bed scanner, a desktop document feed scanner or a higher speed, industrial variation of either scanner. An object to be imaged is typically either moved over the sensing elements (feed-type) or the sensing elements are moved over the object (flat-bed type).
During scanning, defects such as build up of ink, smudges, dust, moisture, etc., on component(s) of the image capture device can cause streaky or defective images. Such defects may occur, for example, in the illumination path between the sensing elements and the object being imaged (e.g., between CCDs and the glass platen) and/or the imaging path through which the sensing elements or object passes (e.g., on the glass platen) and/or on the sensing elements themselves.
In related art devices, imaging non-uniformities are compensated for using the image capture device's calibration process. Typically, image capture device calibration steps alter the video gain and offset so that a uniform emmissivity imaged object produces uniform video. Following calibration, any localized defects caused by the image capture device can result in a locally reduced video value leading to streaky images. Hence, detection of the presence of defects in an image capture device is necessary.
One challenge for detecting when maintenance is required to correct an defect is to be able to distinguish between a streak resulting from hardware, namely the image capture device components, and defects resulting from the object being scanned. Related art devices inadequately address this challenge and, as a result, may give false indications of when maintenance is required to correct a defect in the image capture device.
Another challenge for detecting when maintenance is required is not making premature false indications for problems that may self-correct. For instance, a piece of dust may cause a defect, but the piece of dust may be removed through normal operation of the image capture device, e.g., removal by a subsequent imaged object, aerodynamic activity in an industrial scanner, etc. In certain circumstances, a limited number of defective images created by the piece of dust may be acceptable. In this case, an indication that maintenance is required before the imaging of the acceptable number of objects is unnecessary. Related art devices inadequately address this self-correcting defect challenge and may give premature false indications.
In view of the foregoing, there is a need in the art for defect and maintenance detection in an image capture device that can distinguish between a defect in the image capture device and one on the imaged object.